Necessary to adjust for slurry volume when making a starter?

[SDJay]

I have ~ 600cc of thick slurry, Mr. Malty calculates~ 10% viability. I plan to make a 1L starter, and wasn't sure whether to calculate amount of DME for the 1.6L total or just the initial starter wort.

 

[coopertrooper]

Hi there,

Based on your numbers you have 60ml of viable yeast. Depending on the yeast concentration that you estimate it can range from 1 billion/ml to 4.5 billion/ml.

If you think you are closer to the upper end then you are probably fine (4.5billion *60ml = 270 Billion cells).

If you are really worried, then make a starter. Calculate the DME for a 1L starter size.

If you search google for "yeast starter calculator" the brewersfriend calculator is useful.

Hope this helps,

 

[IslandLizard]

I don't think you can make a good starter with 600 ml slurry and 1 liter wort.
Aside from 90% of the yeast cells being dead, what else is in that slurry? Trub, hop matter?

 

[SDJay]

I don't think you can make a good starter with 600 ml slurry and 1 liter wort.
Aside from 90% of the yeast cells being dead, what else is in that slurry? Trub, hop matter?

I've used similar volumes in the past to directly pitch with slurry that is not as old, but this batch was harvested in December, so rather than throw it out, I thought I'd give it a try. If it flops, I've got an excuse to brew again

 

[IslandLizard]

Aside from Mr. Malty's "pitch from slurry" tab, I use this yeast calculator for my starters:
BrewUnited's Yeast Calculator

I keep a close eye on the various cell values, especially the inoculation rate, keeping that between 25 and 100 million cells per liter of starter wort for optimal growth.

That 600 ml slurry you have, is that the whole or a partial yeast cake from a previous batch? Aside from accumulated trub, if you harvested the whole cake, it contains 4-5x your pitched cell quantity. If it's a partial cake, a proportional amount of that.

Say it's the whole cake, it may have contained 800-1000 billion cells at the end of fermentation (if you pitched ~200 billion, originally). 10% viability would put it at 80-100 billion cells, although that may be a low side estimate. I've pitched 6 months old yeast slurries that took off like a rocket after making a vitality starter, which sounds like what you're planning to make. They're not as much about growth, but to revitalize the live cells in a slurry or fresh pack for better performance and shorter lag times.

Now 600 ml slurry must contain a boatload of trub. You're pitching that too, along with the yeast.